Why is the player still taking fall damage when it's not supposed to?

To put it simply, there is a script inserted into the Humanoid of the player, then there is a LocalScript inside of the PlayerGui that executes this script:

local humanoid = game.Players.LocalPlayer.Character:WaitForChild('Humanoid')
local lowestFallHeight = humanoid:WaitForChild('Impact').lowestFallHeight.Value
local maxFallHeight = humanoid:WaitForChild('Impact').maxFallHeight.Value

local godHealth = math.huge
local currentHealth = humanoid.Health


game:GetService("UserInputService").InputBegan:Connect(function(keyCode)
	if keyCode.keyCode == Enum.KeyCode.LeftAlt or keyCode.keyCode == Enum.KeyCode.RightAlt then
		print('bracing')
		humanoid.MaxHealth = godHealth
		humanoid.Health = godHealth
	end
end)
game:GetService("UserInputService").InputEnded:Connect(function(keyCode)
	if keyCode.keyCode == Enum.KeyCode.LeftAlt or keyCode.keyCode == Enum.KeyCode.RightAlt then
		print('un-braced')
		humanoid.MaxHealth = 100
		humanoid.Health = currentHealth
	end
end)

The script is supposed to completely stop fall damage momentarily, then when the player releases Alt, then the player's health returns back to the original health before they took fall damage.

However, when I test it and fall from a great height and press Alt, the player's health is godded, then when I release Alt, the health returns to the health that was supposed to be taken if it wasn't for the bracing script.

I'm sorry if it's hard to understand, but I hope you do.

Any help please?